JPH0528953Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a switching regulator circuit for boosting or lowering a DC voltage.

(Prior Art) FIG. 4 shows an example of a basic circuit of a switching regulator circuit. In FIG. 2, a transformer 1 has a main winding 1a and a feedback winding 1b on its primary side, and an output winding 1c on its secondary side. The main winding 1a is connected to both ends of a DC power supply 3 via the collector and emitter of a switching transistor 2. The feedback winding 1b is connected between the base and emitter of the transistor 2 via a capacitor 4 and a resistor 5, and is provided to apply positive feedback to the transistor 2 using an induced voltage. In addition, the feedback winding 1
A parallel circuit of a capacitor 9 and a resistor 12 and a series circuit of a diode 10 with the polarity shown are connected to both ends of b, and a constant voltage diode with the polarity shown is connected between the anode of the diode 10 and the base of the transistor 2. 11 is connected. As a result, when the transistor 2 is turned off, the electromotive force e'2 induced in the feedback winding 1b in the direction of the arrow is applied to the capacitor 9 via the diode 10. Further, a rectifying diode 6 and a smoothing capacitor 7 of the illustrated polarity are connected to both ends of the output winding 1c, and loads 13 and 14 are connected to both ends of the capacitor 7. Note that 8 is a resistor connected between the base of the transistor 2 and the positive terminal of the DC power supply 3.

When the transistor 2 is turned off, an electromotive force e′3 in the direction of the arrow is induced in the output winding 1c, a forward voltage is applied to the diode 6, and current is supplied to the load. It becomes like this.

When the supply of the load current _L supplied in this manner is stopped, the base current begins to flow through the transistor 2 due to the back electromotive force appearing in the feedback winding 1b, and in response, the base current starts flowing through the transistor 2 as described above. 2 is turned on. As the transistor 2 is repeatedly turned on and off, the energy E stored in the primary side of the transformer 1 is released to the secondary side. It is possible to obtain an output voltage Eout at a different level from the input voltage Ein.

At this time, the electromotive force e′2 is the electromotive force e′3 of the output winding (that is, the output voltage Eout) and the feedback winding 1
b and the turns ratio of the output winding 1c, and therefore the terminal voltage of the capacitor 9
V′c is proportional to the output voltage Eout. Then, when the output voltage Eout rises and the terminal voltage V'c of the capacitor 9 exceeds the Zener voltage of the Zener diode 11 and breaks over, when the transistor 2 is turned on afterwards, The base current _B supplied to 2 is bypassed by the Zener diode and resistor and is reduced. As a result, transistor 2 is turned off before the collector current c of transistor 2 rises sufficiently, and the energy E stored in transformer 1 decreases, causing output voltage Eout
This operation causes the output voltage Eout to be maintained at a constant voltage.

The operation of the switching regulator configured as described above will be described below.

Now, if base current _B starts to flow through transistor 2 which is in the OFF state, an electromotive force e1 in the direction of the arrow is induced in main winding 1a by collector current c of transistor 2 which flows as a result. The feedback winding 1b also generates an electromotive force in the direction of the arrow.
e2 is induced. This electromotive force e2 is the transistor 2
Since positive feedback is applied by increasing the base current _B of
increases and transistor 2 becomes saturated. At this time, when the collector current c flows through the main winding 1, an electromotive force e3 is induced in the output winding 1c in the direction of the arrow, but since the diode 6 is reverse biased, current flows through the capacitor 7. do not have. Therefore,
Since the load on transistor 2 is only the inductance of transformer 1, the collector current c
increases linearly. Such an increase is stopped in a short time due to insufficient base current _B or DC current amplification factor h _FE after transistor 2 is saturated, and the electromotive forces e1 and e2 are accordingly increased.
becomes zero. In this case, capacitor 5 generates an electromotive force while base current _B flows through transistor 2.
Since it is charged by e2 and the terminal voltage Vc is at a negative level, the transistor 2 is rapidly turned off as the electromotive forces e1 and e2 become zero as described above.

(Problem to be solved by the invention) However, in the above configuration, if there is a large variation in the load of the secondary side circuit connected to the output winding 1c of the transformer 1, the primary side circuit and the secondary side circuit connected to the output winding 1c of the transformer 1 The output voltage on the secondary side fluctuates depending on the energy relationship of the side circuit. That is, in FIG. 4, the load 13
If the load 14 is a light load and the load 14 is a heavy load, and the heavy load 14 can be connected and separated by the switch 15, the output will be smaller when the heavy load 14 is separated by the switch 15 than when it is connected. pressure V ₂
becomes larger. Finally, there was a problem in that the output voltage V ₂ on the secondary side fell outside the range of the specified value V _ON ±ΔV. In order to avoid this, it was necessary to add a new constant voltage circuit.

As a result, the present invention can stabilize the output voltage on the secondary side without installing a new constant voltage circuit even when there are large fluctuations in the load on the secondary side connected to the output winding of the transformer. The purpose of the present invention is to provide a switching regulator circuit.

[Structure of the invention] (Means for solving the problem) In other words, the present invention supplies current from the DC power source to the primary main winding of the transformer while the switching transistor is turned on, and The base current is fed back positively to the transistor through the primary feedback winding of the transformer, and the energy stored in the main winding when the transistor is on is released through the secondary output winding of the transformer when the transistor is off. In the switching regulator circuit configured to A first nonlinear circuit that bypasses a capacitor that is charged via a diode by an electromotive force, and a base current that is positively fed back from the feedback winding to the transistor when the terminal voltage of the capacitor exceeds a predetermined value. a second nonlinear circuit element connected in parallel to the first nonlinear circuit element, and a switch means that is insulated from the voltage detection means that closes when the voltage detection means detects an output voltage equal to or higher than a predetermined value. The configuration includes a series circuit consisting of the following.

(Function) The electromotive force induced in the feedback winding when the transistor is off is proportional to the output voltage from the output winding, and the terminal voltage of the capacitor is also proportional to the output voltage. Therefore, when the output voltage increases and the terminal voltage of the capacitor exceeds a predetermined value, when the transistor is turned on, the base current that is positively fed back to the transistor is bypassed by the first or second nonlinear circuit element. The transistor is turned off early.

At this time, the nonlinear circuit element to which the base current is bypassed differs depending on the output voltage value on the secondary side. For example, when the output voltage value is below a predetermined value, it is bypassed by the first nonlinear circuit element, and when the output voltage value is above a predetermined value, it is bypassed by the second nonlinear circuit element. Bypassed by nonlinear circuit elements. Therefore, even if the output voltage fluctuates due to a large fluctuation in the size of the load connected to the secondary side, this is detected and the switch means is closed, and the base current is transferred to the second nonlinear circuit element. The output voltage can be stabilized according to the load.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Note that in FIGS. 1 and 2, the same parts as in FIG. 4 are given the same numbers and their explanations will be omitted.

That is, in FIG. 1, the capacitor 7 on the output side
In parallel with is a resistor 21, a Zener diode 22,
A series circuit consisting of the light-emitting side 23a of the photocoupler is connected. Also, the light receiving side 23 of the photocoupler
b is the Zener diode 2 which is the second nonlinear element
4 to form a series circuit and connected in parallel to the first Zener diode. and resistance 21,
The Zener diode 22, the light emitting side 23a, and the light receiving side 23b of the photocoupler emit light when the voltage applied to the Zener diode 22 via the resistor 21 exceeds the Zener voltage and breaks over, and the light receiving side 23b of the photocoupler emits light. In response to this, a switch means is formed to close a series circuit with the Zener diode 24.

Here, the Zener voltage of the Zener diode 24 is set lower than the Zener voltage of the Zener diode 11, and in order to maintain the ON state of the light receiving side 23a, the Zener voltage is applied to the Zener diode 22 with the loads 13 and 14 connected. The voltage is selected to be higher than the Zener voltage of the Zener diode 22.

The operation of the switching regulator circuit constructed in this manner will be explained below with reference to FIGS. 2 and 3. Here, FIG. 2 shows a circuit diagram of the main part of FIG. 1, and FIG. 3 is an explanatory diagram of changes in output voltage. Now, assuming that the switch 15 is ON and both the load 13 and the load 14 are connected to the output winding, the output voltage Eout is V _ON . From this state, when the switch 15 is turned OFF and the load 14 is disconnected, the load becomes lighter, and the output voltage increases, exceeding the secondary voltage standard (V _ON +ΔV) of the transformer 1 and reaching V _{OFF.Therefore} , the Zener diode 22
By selecting the Zener voltage value V ₂₂ in the range of V _ON + ΔV > V ₂₂ > V _ON and as close to V _ON as possible, the output voltage can be adjusted to the Zener diode 2.
When the Zener voltage V ₂₂ of 2 is exceeded, a current determined by the resistor 21 flows through the Zener diode 22, the emitting side 23a of the photocoupler 23 emits light, and receiving this light, the light receiving side 23b becomes conductive and the Zener diode 24 is connected in parallel with the Zener diode 11.

Here, the Zener voltage V24 of the Zener diode 24 is the Zener voltage of the Zener diode 11.
Since it is selected to be smaller than V ₁₁ , the Zener diode 24 breaks over first and the base current bypasses it.

Therefore, the base current supplied to transistor 2 decreases, and the output voltage Eout exceeds the secondary voltage standard of transformer 1, V _ON +ΔV, without reaching V _OFF .
V held at ₂₂ .

[Effects of the invention] As explained above, according to the invention, when there is a large load fluctuation on the output side, the fluctuation in the output voltage is detected and the switching transistor connected in series with the main winding of the transformer is activated. By limiting the supplied base current, it is possible to suppress fluctuations in the output voltage and provide a stable output voltage.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of one embodiment of the present invention, Fig. 2 is a circuit diagram for explaining the main parts of Fig. 1, and Fig. 3 shows the output voltage when the load fluctuates in the embodiment of Fig. 1. FIG. 4, which is a diagram explaining the transition, is a circuit diagram showing a conventional example. 1...Transformer, 1a...Main winding, 1b...Feedback winding, 1c...Output winding, 2...Transistor, 9...Capacitor, 10...Diode,
11, 22, 24...nonlinear circuit element, 23...
Phototransistor, 13, 14...Load.

Claims (1)

[Claims for Utility Model Registration] A transformer that has a main winding and a feedback winding on the primary side and an output winding on the secondary side, and a collector current is supplied from a DC power source through the main winding in the on state. and a switching transistor whose base current is positively fed back through the feedback winding, and the energy stored in the main winding when the transistor is on is transferred through the output winding when the transistor is off. In the switching regulator circuit configured to discharge the voltage, the switching regulator circuit includes voltage detection means for detecting that the output voltage on the secondary side has exceeded a predetermined value; a capacitor that is charged via a diode by an electromotive force; and a first nonlinear device that bypasses a base current that is positively fed back from the feedback winding to the transistor when the terminal voltage of the capacitor exceeds a predetermined value. a switch that is insulated from the circuit element, a second nonlinear circuit element connected in parallel to the first nonlinear circuit element, and the voltage detection means that closes when the voltage detection means detects an output voltage equal to or higher than a predetermined value; A switching regulator circuit comprising: a series circuit comprising means; and a switching regulator circuit.